1. Field of the Invention
The present invention relates to a position display apparatus capable of displaying the position of a moving body such as an automobile, ship, aircraft and so forth, suitable for use as, for example, navigation system.
2. Description of the Prior Art
Apparatus for displaying position of a moving body has been known. For instance, Japanese Patent Laid-Open No. 61-75375 discloses a navigation apparatus for use on a vehicle, in which the instant position of the vehicle is computed on the basis of the running distance and direction and is displayed together with map information read from a memory on a display means such as a CRT or an LCD.
Japanese Utility Model Laid-Open No. 56-12300 discloses a moving body position display apparatus in which the instant position is displayed on a matrix display and a map is placed under the matrix display so that the position of the moving body is indicated in relation to the map. According to this arrangement, the magnification of display and the area of display can be altered in accordance with the map so as to enable the use of a plurality of maps. The matrix display is made of a transparent tabular member and is provided with a multiplicity of horizontal and vertical electrodes. When signals are applied to selected vertical and horizontal electrodes, the point of intersection lights up, generates a color or turned opaque. Thus, a plasma display or a liquid crystal display are typically used.
The art of the type disclosed in Japanese Patent Laid-Open No. 61-75375 requires a memory device of a large storage capacity in order to store voluminous map data such as roads, names of streets and towns, addresses and so forth. Thus, there is a practical limit in the number of the maps usable in this system, due to the limit in the storage capacity of the memory device.
On the other hand, the art disclosed in Japanese Utility Model Laid-Open No. 56-12300 requires frequent change of magnification and display area when different maps are used. Therefore, a map having a small resolution has to be used particularly when the vehicle travels a long distance. Conversely, frequent change of map is necessary when a high resolution if required. This necessitates a complicated and troublesome data input operation which involves a large risk of mis-operation.
Accordingly, an object of the present invention is to provide a position display apparatus which is capable of displaying the position of a body carrying the apparatus or the position of an object without requiring the capacity of the memory means to be increased, and which enables an easy set-up of a map in a map book upon replacement of the map book.
Commercially sold map books are usually colored, e.g., in three colors. When such a colored map is used in combination with the display apparatus which utilizes lighting, color generation or opaqueness at the point of intersection of electrodes as in the matrix display shown in Japanese Utility Model Laid-Open No. 56-12300, a problem is caused in that the recognition of the indicated point may be hindered due to similarity of color between the indicated point and the map.
Accordingly, another object of the present invention is to provide a position display apparatus which enables an easy recognition of the position of the body carrying the apparatus or the position of an object.
The apparatus disclosed in Japanese Utility Model Laid-Open No. 56-12300 also encounters a problem in that, since no means is available for informing any deviation of the indication from the correct position due to, for example, a failure in the apparatus, the user may rely upon wrong information.
Accordingly, a further object of the present invention is to provide a position display apparatus which is capable of enabling the user to confirm the coordinates of the measured position, in addition to the recognition of the position information on a map.
A further object of the present invention is to provide a position display apparatus which prevents any erroneous information from being given to the user in the event of a failure in detection of the position.